Pete Brown has a terrific two part series on sensor programming in Windows 7. Part 1 has a link for where to get the board, and fills you in on the new architecture. Lots of helpful links and screenshots here, including one to Pietro Bambrati that includes some changes to the racing game sample to make the accelerometer work and one to his video showing you how to install and test it.
Part 2 starts with this nice summary of your options as a developer:
There are three different ways you can use the accelerometer API. You can, of
course, go directly against the COM API and generate your own wrappers and
pinvokes. You can use the managed wrappers provided in the SDK, or you can use
the Windows API Code Pack which includes support for the sensor
API and a number of other Windows 7-specific enhancements. In this case, I decided to use the code pack in concert with WPF 4.
Hard to argue with that! Pete has written an AccelerometerJoystick you can use in any "controller" situation - and be sure to think beyond just games!
Definitely read and watch, and let Pete and Pietro save you some time!